Performance and stability studies of PtCr/C alloy catalysts for oxygen reduction reaction in low temperature fuel cells

In order to elucidate the reasons for enhanced activity and stability of the alloy catalyst, PtCr/C was prepared by an incipient wetness method and heat-treatments. In single-cell test, the catalysts heat-treated at 900 °C showed the highest performance (about 70% higher than JM Pt/C at 700 mV) because of the alloy effect. Stability of the alloy catalysts was investigated with several accelerated-stress tests. The heavy dissolution of Cr was observed especially in the beginning of operation. The undissolved Cr is considered to take part in the formation of complete alloying. Before and after cell operation, the ratio of Cr to S in the Nafion membrane was measured by EPMA. Within Cr/S of 10% in the Nafion membrane, the conductivity changed a little, but as the Cr/S exceeded more than 10% the serious reduction of conductivity was observed. The catalyst heat-treated at 900 °C showed applicable performance and stability in real cell operations.